PREFACE 
Ten experiments were conducted at the Coastal Engineering Research 
Center (CERC) from 1970 to 1972 as part of an investigation of the Labora- 
tory Effects in Beach Studies (LEBS), to relate wave height variability 
to wave reflection from a movable-bed profile in a wave tank. The inves- 
tigation also identified the effects of other laboratory constraints. 
The work was carried out under the CERC coastal processes program. 
This report (Vol. VI of a series of eight volumes) provides coastal 
engineers who conduct or interpret model studies with an analysis of two 
similar movable-bed experiments that produced different beach changes. 
The analysis suggests that a combination of tank width and wave condi- 
tions caused wave-driven currents to dominate in one experiment but not 
in the other, even though the wave and sand conditions of both experi- 
ments were the same. The currents dominated the experiment run in the 
narrower of two tanks, causing that beach to erode long after the shore 
had stabilized in the wider tank. 
Volume I of this series describes the procedures used in the 10 LEBS 
experiments, and also serves as a guide for conducting realistic coastal 
engineering laboratory studies. Volumes II to VII are data reports on 
the ten experiments; Volume VIII is a final analysis report. 
This report was prepared by Charles B. Chesnutt, principal investiga- 
tor, and Robert P. Stafford, senior technician in charge of the two 
experiments, under the general supervision of Dr. C.J. Galvin, Jr., 
Chief, Coastal Processes Branch. 
Comments on this publication are invited. 
Approved for publication in accordance with Public Law 166, 79th 
Congress, approved 31 July 1945, as supplemented by Public Law 172, 88th 
Congress, approved 7 November 1963. 
| Ve 
y" JOHN H. COUSINS 
Colonel, Corps of Engineers 
Commander and Director 
